(2/5y-0.5x)(0.5y+2/5y)

(2/5y-0.5x)(0.5y+2/5y) x-y=2 那么-2x-2y=多少[（2x=y)的平方-（2x+y)(2x-y)-y(5x+y)]/(0.5y),其中x-y=2 (x-5y)(-x-5y)-(-x+5y)^2,其中x=0.5,y=-1.计算 (x-5y)(-x-5y)-(-x-5y)^2其中x=-1,y=-0.5 二元一次方程组 X-Y/7-X+Y=0.5 2(X-Y)+5(X+Y)=3 5x(x-y)+2y(x-y) 化简:5(x-y)+2(x+y)-3(x-y) 已知x：y=0.5:0.3,y:z=1/5:1/2,求x:y: 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) （X+2Y)(5X-2Y) (x+2y)(5x-2y) 4x+2y-5x-y (2x-3y)-(5x-y) (2X-3y)-(5x-y) (x-y)^2+5(x-y)-14 (2x-5y)(3x+y) 因式分解(x-2y)(x-3y)+(x-4y)(x-5y)+（x-3y)(x-5y)+(x-2y)(x-4y) [2(x-y)^5-8(x-y)^2(x+y)+6y(x-y)^2]÷2(x-y)^2[2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2]÷2(x-y)^2